OFFSET
0,3
FORMULA
E.g.f.: B(x)^3, where B(x) is the e.g.f. of A371143.
a(n) = 3 * n! * Sum_{k=0..floor(n/2)} (3*k+2)! * Stirling2(n-k,k)/( (n-k)! * (2*k+3)! ).
PROG
(PARI) a(n) = 3*n!*sum(k=0, n\2, (3*k+2)!*stirling(n-k, k, 2)/((n-k)!*(2*k+3)!));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Nov 04 2024
STATUS
approved